Overview: Matroska family
Matroska and WebM share a container foundation while defining different permitted media combinations and conventions.
Matroska can organize multiple kinds of tracks and supporting information in one container. WebM builds on that foundation with a more constrained format definition. Comparing the two is useful when a familiar-looking file needs to work in a particular player or delivery environment; the track codecs remain part of that decision.
Matroska (MKV and MKA)
Matroska stores multiple encoded tracks, timing information, and optional chapters and attachments in an extensible media container.WebM
WebM is a constrained Matroska-based container designed for web delivery of encoded video and audio.